doc/next: improve new(expr) release note
One reader pointed out that the example isn't compelling because
&age would have worked just as well. This CL changes the example
to use a nontrivial expression. Don't nitpick the arithmetic.
For #45624
Change-Id: Icc745f5ee7000c1d3559da1388c6a5596c4d1f46
Reviewed-on: https://go-review.googlesource.com/c/go/+/714040
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>